Measuring an alignment target with a single polarization state
US6992764B1 · kind B1 · utility
Assignee
Inventors
Key dates
| Filing date | Sep 30, 2002 |
| Grant date | Jan 31, 2006 |
| Priority date | — |
| Expiry date | Nov 23, 2023 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01N2021/4792
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
An alignment target includes periodic patterns on two elements. The periodic patterns are aligned when the two elements are properly aligned. By measuring the two periodic patterns with an incident beam having a single polarization state and detecting the intensity of the resulting polarized light, it can be determined if the two elements are aligned. The same polarization state may be detected as is incident or different polarization states may be used. A reference measurement location may be used that includes a third periodic pattern on the first element and a fourth periodic pattern on the second element, which have a designed in offset, i.e., an offset when there is an offset of a known magnitude when the first and second element are properly aligned. The reference measurement location is similarly measured with a single polarization state.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.